Tube electrode



1966 D, R. KERSTETTER 3,252,044

TUBE ELECTRODE Filed July 20, 1962 2 Sheets-Sheet 1 VAR/ABLE AIR SUPPLY INVENTOR Donald R Ke/sfezfer (QM/ Ma ATTbRNEY May 17, 1966 D. R. KERSTETTER 3,252,044

TUBE ELECTRODE Filed July 20, 1962 2 ShGEtS -SI'IGEt 2 TENS/ONAL FORCE-GM a0 /00 K /WRAPPED LENGTH OF HELIX L f LU U \f i1 J TURN LENGTH OF HELIX INVENTOR ATTo'RNEY This invention generally relates to a process for Wrap- Y ping a support with a helix of wire and more particularly to the use of this process in frame type grid electrodes for electron tubes.

In a process of winding a helix of wire about a support and especially in the manufacture'of frame grid electrodes, it has become increasingly evident that the tension exerted between the side members and the wire helix traversing them is of utmost importance. When tube electrodes are closely spaced and small in size, the materials used in the structure lack the physical strength present in the former self-supporting type of electrodes. As a consequence, problems growing out of inwardly bowed side members, loose and sagging wires surrounding the si e members, and broken wires both during and after the wrapping process have plagued the manufacture of frame grid electrodes. Although numerous variations and alterations have been made in the materials and Wrapping process to improve the tension relationship between side members and the lateral wire, the control level thus far achieved has not been adequate.

One approach to the tension problem when using a selfsupporting type electrode utilizes a fixed amount of back tension which is applied to the lateral wire as it is wrapped about the spaced side members. While the technique has proven satisfactory for heavier and physically stronger materials or wires, it has several disadvantages when lighter and more easily distorted materials are used. Those disadvantages will be appreciated when it is realized that since the lateral wire helix surrounding the side members is attached thereto only at the ends of the helix, the intermediate lateral turns are held in position only by the frictional forceexisting between the side members and the wire. Therefore, it is imperative that the wire have suflicient back tension during the wrapping process to correctly position and retain each lateral wire turn on the side members.

It has been found that an insufiicient amount of fixed back tension or opposition to the pull on the Wire during a wrapping process results in erratic and poor spacing between adjacent turns of the electrode. Further, if the back tension is insufiicient during the wrapping process, the tension developed between the wire helix and the side members permits the wire turns to sag during tube operation. As a result, the desired electrical characteristics are lost and reliability of the electron discharge device is reduced. Additionally when the wire turns surrounding the side members are not taut, their vibration characteris- United States Patent tics result in microphonic and uncontrollable noise factors which are again detrimental to product reliability.

Conversely, when the fixed back tension on the lateral wire during wrapping is increased to a level just below the breaking point of the lateral wire, the side niembeTs progressively bow inwardly as successive lateral wire turns are added to the helix. It is to be realized that when the spaced side members are rigidly held by cross straps outside of the helix area, the bending moment exerted on the side members increases as each turn of the helix is i added. This condition occurs even through the actual back tension or force exerted by each turn of the wire remains fixed. Therefore, the side members intermediate the rigid cross straps how more inwardly with each succeeding turn. As a result, the tension between the side 3,252,044 Patented May 17, 1966 member and the previous turn is lost and these turns become losse and sag from their original location.

In addition to the previously mentioned problems, it has also been found that the widely used non-circular type of wire helix grid requires a varying supply of lateral wire. It should be realized that when a pair of spaced side members for a non-circular grid are rotated to cause the lateral wire to wrap thereabout, the lateral wire will be demanded at a varying cyclic rate by the side members which may be rotating at a constant rate. This cyclic demand for lateral Wire at the side rods causes unwanted varying back tension on the wire.

Attempts to correct this problem primarily have been directed toward providing a dampening device intermediate the lateral wire supply and the side member wrapping location. Various combinations of pulleys, weights, and springs have provided very limited success in attempts to eliminate cyclic back tension lateral wire variations. This limited success is believed to be based upon the fact that the inertia of the dampening apparatus itself prevents the rapid variations in response necessary to compensate for the rapid changes in tension and lateral wire demand by the rotating side members.

Therefore, it is an object of the invention to improve the reliability of a helix wrapped support grid.

Another object of this invention is to reduce the variations along the helix in the tensional force between the wire turns and the spaced side members.

A further object of the invention is to improve the microphonic and random noise characteristics of an electrode for an electron discharge device.

A still further object is toreduce the cyclic back tension variations in wire supplied to the spaced side members during a wrapping process.

An additional object of this invention is to program the back tension force on the lateral wire during the wrapping process to provide a wrapped grid having multiple turns of wire with each turn exhibiting substantially the same tension characteristics.

The foregoing objects are achieved in one aspect of the invention by programming the variation in back tension on the lateral wire as it is wrapped about the support. The desired program Varies the back tension on the wire as the turns of a wire helix wrap about the rotating side members in accordance with the cumulative deflection forces on the side members exerted by the summation of individual turn forces exerted during winding the completed helix. This tensional relationship is provided by synchronizing a programmed back tension cam with the side member rotating device. In addition, a low inertia dampening device may be employed so that the varying rate of wire demand by the rotating side members during the wrapping of each turn may be substantially immediately met. The dampening device has low mass and low inertia to facilitate substantially instantaneous response to variations in wire demand by the rotating side members.

For a better understanding of the present invention, together with other and further objects, advantages and capabilities thereof, reference is made to the following disclosure and appended claims in connection with the accompanying drawings in which:

FIG. 1 is a perspective view FIG. 2 is a curve of the bending moment and the lateral turn tensional force of an electrode wrapped with a uniform back tensional force; and FIG. 3 is a curve of the programmed back tensional force applied to the wire and the resulting cumulative tensional force exerted by the lateral turns on the side members; and

FIG. 4 is a curve of the wire demand by the side of a strap frame; and

members during rotation and wire deflection by the low inertia dampening device; and

FIG. 5 is a diagrammatic view of a programmed back 1 tension wrapping apparatus and a low inertia dampening devicepand FIG. 6 is a diagrammatic view of a completed strap frame grid electrode with the wire turn-s wrapped thereabout and affixed thereto.

The most frequently encountered prior art is that in which a' strap 'frame which will be described later is wrapped with a wire helix to provide a strap frame electrode. During this wrapping process, a uniform back tensional force is applied to the wire from which the helix is formed. It is believed that the cumulative bending moment exerted upon the side members by the wire helix turns when applied with a uniform back tensional force on the wire varies substantially as shown in curve A of FIG.

2. Further, it has been found that the tensional force exerted between the side members and the lateral wire turns varies substantially as shown in curve B of FIG. 2. Accordingly, this process results in loose and sagging lateral wire turns especially in the areas where the tensional force is low which permit the electrical characteristics controlled by the grid electrode to vary and the micnophonic and random noise values to increase.

A process which has substantially reduced these problems and aided greatly in the manufacture of reliable electrodes is the application of a programmed back tensional force to the lateral Wire during the wrapping process. in this process the tension may be pro-selected for each turn of the'wire helix and increased or decreased in substantially any prescribed manner desired. As is well known, when a force is applied to a wire within the elastic limit thereof, the wire will react in a substantially expected and predictable manner. Accordingly, a back tensional force, curve C .of FIG. 3, is applied to the wire within the elastic limit thereof which is substantially proportional to the cumulative deflection force exerted by all of the completed helix turns on the side members and the tensional force desired on each turn upon completion of the helix. As a result, the side members bow sufiiciently to'relieve the tensional force added to each turn to compensate for this how and the desired uniform tension on each turn remains substantially as pre-selec-ted, curve D of FIG. 3. Moreover, the back tensional force may be pre-selec-ted to provide substantially any desired variation or level of tensional force between the helix and the side members. 7

Additionally, when a pair of spaced side members such as a strap frame is wrapped with a wire helix having a noncircular periphery, it has been found that intermittent periods of increased wire demand by the rotating side members occur. Further, this increased wire demand occurs not at the frequency of rotation but at twice the frequency of rotation. Moreover, the periods of increased wire demand are interspersed with periods when the wire demand is not as great. Thus it has been found that the variation in wire demanded by the rotating side members.

varies substantially in a sinusoidal pattern throughout the longitudinal length of the helix as shown by curve E of FIG. 4. 1

Accordingly, a low inertia dampening device which will be described-later may be inserted intermediate the wire supply source and the rotating side members. This device provides a resilient elastic force such as a fluid force, electrostatic force, magnetic force or numerous other mediums which act upon thewire and cause a deflection thereof substantially as shown in curve F of FIG. 4. Thus, as the wire demand by the rotating side members increases, the deflection of the wire intermediate the supply source and the rotating side members decreases whereupon'the increased demand is substantially immediately supplied. Further, when the wire demand decreases the wire deflection increases whereupon the supply of wire available at the rotating side members is decreased.

Therefore, each turn of the wire helix has a substantially uniform tensional force exerted thereon throughout the entire winding length of the turn regardless of the speed at which the turns are applied to the side members.

In a process for wrapping the strap frame of FIG. 1 to form the strap frame electrode of FIG. 6, an apparatus as illustrated in FIG. 5 may be used. An automatic grid electrode winding machine having a rotating headportion 13 is synchronously operated with wire guide 15 and programmed tension means 17. Additionally, low inertia dampening apparatus 19 may be disposed adjacent to but not geared or synchronously connected with the grid electrode wrapping apparatus.

The rotating head portion 13 of the grid electrode machine is stationary in the loading position and the strap frame of FIGQI is loaded thereon. Rotating head portion 13 then moves to the operating position whereat it remains stationary until the wire which forms the wire helix is fed from a supply source affixed to back tension means 17 onto wire guide. 15 and to the strap frame.

FIG. 1 positioned on rotating head portion 13 whereat the wire is attached. Rotating head portion 13 is then activated whereupon the wire attached thereto wraps about the strap frame of FIG. 1. synchronously oper ated wire guide 15 acting through appropriate linkages and contoured cams directs the wire longitudinally along the strap frame at a rate and spacing between wrapped turns which may be pre-selected. Simultaneously, programmed back tension means 17 operating through the necessary linkages and contoured cams provides a predetermined varying tensional force in opposition to the flow of wire from the supply source to rotating head portion 13 whereat the wire forms the helix surrounding the strap frame. When the desired helix length has been wrapped upon the strap frame, the rotating head portion is stopped and the wire from the supply source is again attached to the strap frame and subsequently severed immediately adjacent thereto. Rotating head portion then returns to the loading position whereat a frame grid electrode as shown in FIG. 6 is removed therefrom. Accordingly, a rotating head portion 13, a programmed back tension means 17, and a wire guide 15 operating in syn chronous relationship provide a process wherein the spacing between adjacent turns of a wire helix wrapped upon a strap frame may be pre-selected and the back tensional force exerted on the wire throughout the helix formation and consequently the tensional force exerted between each wire turn of the helix and the strap frame side members may be pro-determined and controlled.

Additionally, low inertia dampening device 19 may be used in conjunction with the above stated process and apparatus as shown in FIG. 2. Dampening device 19 may be disposed intermediate the wire supply source of programmed back tension means 17 and wire guide 15. As wire is demanded for wrapping the wire helix upon the strap frame at rotating head portion 13, the wire is withdrawn from programmed back tension means 17. Dampening device 19 provides an elastic resilient deflecting force normal to the wire intermediate the supply and the demand. When the demand for wire at rotating head portion decreases, the tensional pull on the wire decreases and the low inertia dampening force provides a substantially immediate increased deflection of the wire thereby decreasing the wire supply at the rotating head portion 13 and returning the tensional pull to its previous value. Further, when the wire demand at rotating head portion 13 increases, the tensional pull on the wire is increased and is met by an inversely proportional decrease in deflection by low inertia dampening device 19. Accordingly, low inertia dampening device 19 provides a force normal to the wire flow during the wrapping of the wire on a strap frame whereby a change in wire demand is met by an inversely proportional and substantially immediate change in wire deflection and as a result, each helix turn is wrapped with a substantially uniform tensional force throughout its length regardless of the variations in wire demand or' rotational speed which occur during the wrapping process.

A programmed back tension apparatus is shown in FIG. 5 whereby the strap frame of FIG. 1 may be wrapped with a wire helix to form the frame grid electrode of FIG. 6. An automatic grid electrode wrapping machine is provided with a rotating head portion 13 which is synchronously operated wtih a wire guide 15 and programmed back tension means 17. Additionally, low inertia dampening means 19 may be disposed adjacent the programmed back tension apparatus and operated in conjunction therewith but need not be attached thereto.

FIG. 1 shows a strap frame 5 prior to the addition of the wire helix. It is the turns of the wire helix wrapped upon the strap frame 5 which form a frame grid electrode as shown in FIG. 6. The side members 7 are rigidly spaced by pairs of supporting cross straps 9 at each end and may be round rectangular, formed, or numerous other configurations. The cross straps 9 are attached to the side members 7 in numerous ways such as brazing, or fritting but in this specific instance, welding has proven most satisfactory. The inside surface 9 and the inside surface of the sidemembers 7 form a channel 10 through which may be inserted a support means for holding the strap frame 5 while the helix of Wire is wrapped as will hereafter be described.

of the cross straps- FIG. 6 shows the strap frame 5 of FIG. 1 with the wire helix 8 wrapped thereon to form a strap frame grid elec trode. The wire helix 8 has n-turnsbf lateral wire and each turn frictionally engages side members 7. Also the ends 12 of Wire helix 8 are secured at longitudinally opposite ends of strap frame 5. Side members 7 have a maximum inward deflection at n/Z-position 14 due to the cumulative force of n-turns acting thereon.

A rotating head portion 13 of a strap grid electrode winding machine is shown having diametrically opposing heads 21 and 23 which may be rotationally driven either individually or jointly during the strap frame wrapping process. Head 23 having a face portion 27 with mandrel 25 projecting therefrom has a loading position, shown by the dotted lines, and an operating position, shown by the full lines and means (notshown) whereby movement of head 23 from the loading position to the operating position is accomplished. Mandrel 25 is machined to provide a tightly fitting support for the frame 5 when telescoped through the channel 10 shown in FIG. 1. A tapered end 26 of mandrel 25 facilitates the loading of strap frame 5 thereon. Head 21 has a recessed portion (not shown) wherein the tapered end 25 of mandrel 25 is adapted to fit when head 23 moves forward to the operating position, shown in full lines. The engagement of tapered end 26 of head 23 with the recessed portion (not shown) of head 21 during rotation provides a firm support for mandrel 25 and strap frame 5 telescoped thereon. While in the operating position, Wire 41 is attached to strap frame 5 and upon rotation of heads 21 and 23 wraps about frame 5.

The wire guide 15 is provided with wire guide arm 37 which is driven by drive means 31 through a shaft 33, guide cam 29, and guide cam follower 35. Further, a wire slot 39 is provided at the end of wire guide arm 37 for correctly positioning the wire 41 on wire guide arm 37 during operation. Wire guide cam 29 is contoured .to provide any desired rate or variation in helix turn spacing as it longitudinally drives wire guide arm 27 and wire slot 39 through which wire 41 is directed onto strap frame 5. Wire guide spring 43 connecting wire guide arm 37 and fixed wire guide spring support 44 assures positive contact of guide cam follower on guide cam 29 thereby insuring correct longitudinal positioning of each helix turn on frame 5.

The programmed back tension means 17 has a 400- cycle back tension motor 55 driven from a conventional power source through an amplifier 57 having a voltage control 59. A variable center tap arm 61 on the voltage control 59 is activated through a sliding arm 47, programmed cam follower 49, a programmed cam 45, a shaft 33, and drive means 31. A tension spring 53 and a fixed tension spring support 54 provide positive action between the programmed cam follower 49 and the programmed cam 45. The shaft 65 of the back tension motor 55 is inserted within and frictionally holds a wire supply spool 63 from which wire 41 is withdrawn by strap frame 5 as it is rotated 'by rotating heads portion 13 to form the frame grid electrode of FIG. 6.

When the voltage on the back tension motor 44 is varied, the force exerted on the wire 41 through the shaft 65 and supply spool 63 is also varied. As a result, the back tension force or force opposing the withdrawal of wire 41 from the supply spool'63 may be controlled.

Therefore, when the center tap arm 61 is varied through the slide 47, and programmed cam follower 49 by rotation of the programmed cam 45, the back tension on wire 41 is also varied. Thus, the programmed cam 45 may be formed to provide the desired variations of the center tap arm 61 which essentially controls the'amount of back tension opposing the withdrawal of wire 41 from the supply spool 63 and in turn the tension on wire 41 as the turns are applied to the strap frame of FIG. 1.

The loW inertia dampening means 19 has an exhaust vent 79 which is supplied with air from a variable air supply 75 through an interconnecting pipe 77. This eX- haust vent 79 is positioned directly beneath the wire 41 intermediate the wire supply spool 63 and the wire guide slot 39. A fiat thin gage foil 67 is afiixed to a fixed support at one end 69 immediately adjacent the exhaust vent 79. The opposite curved portion 71 of the flat foil 67 is provided with a wire guiding groove 73 and is disposed immediately above the exhaust vent 79 with the wire guiding groove 73 contiguous With the wire 41. Therefore, the Wire 41 and the curved portion 71 of the flat foil 67 are supported by the force of air issued from the exhaust vent 79. As pressure is exerted by the wire 41, fiat foil 67 which is supported by the air emitted from the exhaust vent 79, is deflected. Hence any change in wire demand by the rotating strap frame 5 is substantially immediately met by a deflection of the flat foil 67. Accordingly, an increased wire demand provides an increased tension pull on the wire and results in a decreased wire deflection resulting in an increased supply to meet the increased demand. Since this deflection change is substantially immediate, the tension on the wire throughout the length of each turn remains substantially constant.

Accordingly, the proper selection of a programmed back tension cam profile has permitted a reduction in the forces exerted upon the wire and the side members during the wrapping process of approximately 40% while producing an improved product. Further, the variations in tensional force exerted between the side members and the wire of the resulting strap frame electrode have been reduced by approximately 70%. Therefore, a pair of spaced side members wrapped with a wire helix having a substantially uniform tensional force exerted throughout the longitudinal length of the helix provides an electrode of greatly improved reliability. Additionally, the reduced tensional forces substantially obsolete the former requirements of strong, expensive and hard-to-work materials for strap-frame electrode manufacture. Rather, less strong, readily available, inexpensive, and more workable materials may now be used to provide a product of vastly improved reliability at a tremendously reduced cost. Furthermore, the uniformity of tensional forces has greatly improved the microphonic and random noise characteristics by virtually eliminating loose and vibrating lateral turns whereby the operational reliability of the strap-frame is enhanced. Additionally, a resilient elastic low inertia dampening device provides a uniform tensional 7 force throughout the entire length of each helix turn during the wrapping thereof.

Although the back tension and dampening techniques described herein have been specifically illustrated in conjunction with a strap-frame electrode, it is to be understood that the invention is not limited thereto and may be used on any type construction wherein a support and wire strands or wire Win-dings have a tensional relationship.

While there has been shown and described what are at present considered to be the preferred embodiments of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the scope of the invention as defined by the appended claims.

What is claimed is:

1. A process for wrapping a given length of apair of spaced side members with a helix of Wire comprising the steps of attaching the wire at one end of said side members, wrapping said given length of said spaced side members with the wire helix while applying a programmed back tension force to said wire during winding which rises to a maxi-mum at a position intermediate the midpoint thereof and said one end and substantially uniformly decreases from said intermediate position to the end of the wire helix, and attaching the Wire at the opposite end of said side members to provide a substantially uniform tensional force on the Wire turns of said helix throughout'the given length.

2. A process for wrapping a frame with a helix of Wire, said frame having spaced side members and spaced supports spanning said side members and afiixed thereto comprising the steps of attaching the wire at one end of said frame, wrapping said side members intermediate said supports with the wire helix while applying a programmed back tension force to said wire during Winding which reaches a maximum at a position intermediate the midpoint thereof and said attached end and decreases from said maximum position in preselected amounts at pro-selected intervals to the end of the wire helix, and attaching the wire at the opposite end of said frame to provide a substantially uniform tensional force on the Wire turns of said helix throughout the total helix length.

3. A frame electrode comprising a frame including a pair of spaced side members each having the ends thereof lying along a given axis and a pair of spaced supports spanning and afiixed to said side members, and a tensional wire helix of n=turns Wrapped about said side members intermediate said spaced supports, said helix having a first and second end attached to said frame and having a programmed b ack tension force exerted there-on during Wrapping which rises to a maximum at a point substantially intermediate said first end and the midpoint thereof and decreases from said point to said second end, whereby each turn has a substantially uniform tensioned force throughout the. length of the helix.

References Cited by the Examiner UNITED STATES PATENTS 1,642,498 9/ 1927 Houskeeper 313-3511 1,719,774 7/1929 Metcalf 313-9350 1,957,223 5/1934 Murphy "-1., 313'350 2,181,288 11/1939 Washburn 140-715 2,581,876. 1/1952 Parker 313348 2,657,868' 11/1953 Breazeale 2 242-45 3,054,430 9/1962 VanTol et al. 140'71.5 3,069,585 12/1962 Katz 313-348 3,081,800 3/ 1963 Crosby et al 140-715 FOREIGN PATENTS 1,212,582 3/ 1960 France.

963,260 5/ 1957 Germany. 1,019,011 11/1957 Germany.

JOHN W. HUCKERT, Primary Examiner;

JAMES D. KALLAM, DAVID J. GALVIN, C. E. PUGH,

Assistant Examiners. 

3. A FRAME ELECTRODE COMPRISING A FRAME INCLUDING A PAIR OF SPACED SIDE MEMBERS EACH HAVING THE ENDS THEREOF LYING ALONG A GIVEN AXIS AND A PAIR OF SPACED SUPPORTS SPANNING AND AFFIXED TO SAID MEMBERS, AND A TENSIONAL WIRE HELIX OF N-TURNS WRAPPED ABOUT SAID SIDE MEMBERS INTERMEDIATE SAID SPACED SUPPORTS, SAID HELIX HAVING A FIRST AND SECOND END ATTACHED TO SAID FRAME AND HAVING A PROGRAMMED BACK TENSION FORCE EXERTED THEREON DURING WRAPPING WHICH RISES TO A MAXIMUM AT A POINT SUBSTANTIALLY INTERMEDIATE SAID FIRST END AND THE MIDPOINT THEREOF AND DECREASES FROM SAID POINT TO SAID SECOND END, WHEREBY EACH TURN HAS A SUBSTANTIALLY UNIFORM TENSIONED FORCE THROUGHOUT THE LENGTH OF THE HELIX. 